1. Field of the Invention
The present invention relates to a system for determining the compression ratio at which an engine is operating. The present system is particularly adapted for use with a connecting rod for a reciprocating internal combustion engine in which the effective length of the connecting rod may be controllably varied so as to change the compression ratio of the engine.
2. Disclosure Information
Students of thermodynamics understand that, in general, higher compression ratios yield higher thermal efficiency for piston-type internal combustion engines. Unfortunately, with premixed charge engines, most commonly sold in the form of spark-ignited engines operated on gasoline, higher compression ratios may cause problems arising from pre-ignition. This problem may be exacerbated, moreover, when an engine is turbocharged or super-charged. Therefore, it would be desirable to have an engine which can normally be operated at a higher compression ratio at most operating conditions, so as to yield maximum fuel economy, while still allowing operation at lower compression ratio at the highest power conditions. This would allow the engine to produce maximum power without knock or preignition. The inventor of the present connecting rod and compression ratio measuring system provides a unique solution to problems associated with known variable compression ratio arrangements. Such arrangements as pistons with variable compression height, typically developed by BICERI, as well as a variable plethora of other mechanical devices all suffer from problems relating to controllability, inadequate time response, excessive weight, excessive complexity, and other issues. One of the additional issues deals with the determination, in real time, of the compression ratio at which the engine is operating. U.S. Pat. No. 4,834,031 discloses a pressure sensor for determining the compression ratio of an engine by directly measuring the pressure within the combustion chamber. The system of the '031 patent is an analog device which is excessively expensive and which may suffer from ambiguities arising from the need to factor in many variables to determine the pressure range attributable to various compression ratios. The present compression ratio measuring system, which is mated to a variable length connecting rod, solves the problems associated with prior compression ratio controlling devices by using a robust digital device which produces a signal having a variable duration which is clearly linked to the compression ratio at which the engine is operating.